We had also investigated the differences in fingerprintability between HTTP/QUIC and HTTPS (WF in the Age of QUIC, PETS'21). We had found equivalent fingerprintability with deep-learning classifiers when eavesdropping on the traffic through Wireguard. It's interesting though to see the stark difference they found between fingerprinting HTTP/QUIC and HTTPS when using only the first ~40 packets. The trends in those early packets had also allowed us to easily differentiate between the two types of traffic over the VPN.
Our paper, in case you want to read more on this area: https://petsymposium.org/2021/files/papers/issue2/popets-202...